There is a "/proc/self/exe" support under GNU/kFreeBSD, but it is limited, namely inside combination of bind mounts and chroots.
It is possible that this is a linuxism, but if this should not be used on bsd, wouldn't it be better if the proc filesystem is NOT available on the porter boxes? Or at least document it so that package maintainers can find it. I do not see proc mentioned here
To clarify: The GNU/kFreeBSD provides /proc, but some details are not the same as on Linux. And some part work in the same way only under usual configuration. The /proc is used for "ps", therefore it should be mounted, but i.e. readlink of /proc/self/exe is not the right way to get full path to executable. Issue with /proc/self/exe is not the common porting problem, in fact I do not remember happening it in the past.
Petr